Electronic fuel injecting system for internal combustion engines

ABSTRACT

A fuel injecting system providing an accurate adjustment of the duration of injection, the operative cycle being subdivided into a first stage during which the energy required for injection or the corresponding information is stored in a condenser which is discharged during the second or injection stage. The shifting from one stage to the other is controlled by two switches constituted by transistors acting in alternation so as to energize during a predetermined stage a unijunction transistor controlling the starting and stopping of the injection in conformity with a number of parameters stored in memories. The original signals fed into the system are advantageously produced by an oscillator operating for predetermined angular positions of the crankshaft.

United States Patent 1 1 Monpetit 1 1] 1 3,744,460 1 July 10, 1973ELECTRONIC FUEL INJECTING SYSTEM FOR INTERNAL COMBUSTION ENGINES [75]Inventor: Louis Monpetit, LEtang La Ville,

France [22] Filed: Apr. 21, 1971 [21] Appl. No.: 136,002

[30] Foreign Application Priority Data Apr. 28, 1970 France 7015452 [52]US. Cl. 123/32 EA,'123/119, 123/140 MC [51'] Int. Cl. F02b 3/00 1 [58]Field of Search 123/32 AB, 32 EA,

[56] References 'Cited UNITED STATES PATENTS 3,620,196 Wessel 123/32 EA3,534,719 10/1970 Minks ..123/148E Att0rneyKeny0n 8L Kenyon Reilly Carr& Chapin 57 I ABSTRACT A fuel injecting system providing an accurateadjustment of the duration of injection, the operative cycle beingsubdivided into a first stage during which the energy required forinjection or the corresponding information is stored in a condenserwhich is discharged during the second or injection stage. The shiftingfrom one stage to the other is controlled by two switches constitutedbyv transistors acting in alternation so as to energize during apredetermined stage a unijunction transistor controlling the startingand stopping of the injection in conformity with a number of parametersstored in memories, The original signals fed into the system areadvantageously produced by an oscillator operating for predeterminedangular positions of the crankshaft.

11 Claims, 4 Drawing Figures PAIENIEU v 3.744.460

' sum 1 or 4 I //v vewmq Lows 14. Moupsrn mmmvexs ELECTRONIC FUELINJECTING SYSTEM FOR INTERNAL COMBUSTION ENGINES The present inventionhas for its object improvements in electronic control systems for theinjection of fuel into internal combustion engines. Such systems, asknown hitherto, rely almost all on the principle that the amount of fuelto be defined with reference to the operative conditions of the enginedepends on the one hand on the injection pressure, assumed to beconstant and on the other hand on the duration of the electric signaltransmitted to the electromagnetic solenoid actuated fuel injectionvalves. To this end, there is provided in the French Pat. No. 1, 172,680 a monostable flip-flop triggered by a detector pulse generatorcontrolled by the rotation of the engine so as to produce rectangularsignals in synchronism with said rotation and the durations of which areadjusted in accordance with the operative conditions of the engine.These signals are then applied to the solenoid-actuated fuel injectorvalve through amplifier. Such arrangements provide an accurate timingsince injection begins when the flip-flop is triggered and the injectionduration is determined in accordance with prevailing operative enginecondi tions.

Although such arrangements seem at first very simple, yet they becomevery intricate when it is attempted to match accurately the requirementsof a particular engine, chiefly with a view to reducing the pollution ofthe atmosphere by the exhaust gases of the engine. As a matter of fact,the actual fuel requirements are by no means independent of the speed ofrotation of the engine and depend in accordance with an intricate law onthe rotary speed of the engine, on the extentof the opening of the gasthrottling valve and, on the reduction in pressure in the admissionmanifold. Said law depends also on the ambient temperature, on thetemperature of the engine and on the barometric pressure and it variesalso according as to whether the engine revolves at a stabilized,accelerated or decelerated speed. Furthermore, since the parametersensors defining the duration of injection can show only average valuescorresponding to the duration of injection, it is necessary to make usethereof in a manner such that these average values may correspond to thecharacteristic properties of the engine prevailing at a well-definedmoment of the injection.

It is therefore apparent that it is necessary to provide a multiplicityof auxiliary circuits adapted to ensure the formation of an input signalfor the monostable flipflop which accurately represents the condition ofthe engine.

On the other hand, U.S. Pat. No. 2 ,018, 159, inter alia, disclosesstoring, as a first step, of an amount of energy which depends on theoperative conditions of the engine, while said energy is released as asecond stage step, to control the opening of an electromagnetic injectorfor a period corresponding to the amount of energy stored. To this end,there is disclosed in said .last-mentioned patent a first switchactuated in synchronism with the rotation of the engine so as to chargea variable condenser through a variable resistance while a second switchthen connects the charged condenser with the electromagnetic injectors.Obviously, such an arrangement could not operate reliably or durablysince the mechanical contact-pieces wear rapidly. Furthermore, thearrangement as designed could not 5 jectors.

provide a sufficient adjustment of the duration of injection, all themore so since the closing of the injectors was certain by reason of thefact that the limit closing current may vary to alarge extent for thedifferent in- The present invention has as its object the elimination ofthe drawbacks of both above mentioned injection systems by providing animproved arrangement for the electronic control of a fuel injectingsystem for internal combustion engines including one or moreelectromagnetic injection valves. The present system is of the typewherein the electric energy controlling the electromagnetic valves and/or the electric information corresponding to the duration ofenergization and con sequently to the amount of injected fuel, is storedin a suitable circuit section during a first period of the operativecycle of the engine, said energy and/or the information being thenreleased during a further period of the operative cycle in order tocontrol the injection. According to the invention, the arrangement isconstituted by a condenser adapted to store the energy required forinjection and/or the information and connected between a constant supplyvoltage and a vari-' able relatively low voltage supply under control ofa first switch as provided by a least one memory and as governed by theoperative conditions of the engine. This first switch is connected withmeans sensitive to the angular position of the crankshaft forcontrolling the charging of the condenser at the low voltage during thestoring period. A threshold element provided with a plurality of inputsis also provided, which is connected on the one hand with the condenserand on the other hand with a supply of a variable positive voltagethrough another memory, under the control of the operative parameters ofthe engine, last-mentioned said voltage defining the triggeringthreshold of said element. The condenser is discharged during theinjection period by a second switch which is then released and is lockedduring the storing period. An amplifier is also provided for the controlof the electromagnetic valve or valves and is connected withthe secondswitch and with the threshold element, said second switch controllingthrough this last connection the beginning of the injection while saidthreshold element controls its end when the condenser is discharged downto a certain voltage corresponding to the triggering threshold of saidthreshold element.

Withsuch an arrangement, it is possible to utilize simple circuitshaving the capability to introduce a mu]- tiplicity of independentparameters, primarily engine speed, through the use of memories withoutresort to special circuit elements such as tachometers or centrifugallycontrolled rheostats. Furthermore, the present invention is particularlysuited to the use of integrated circuits for effecting its variousfunctions.

Although the invention is embodied in an arrangeabout 10 milliseconds.In prior systems incorporating 4 monostable flip-flops, the injectionperiod equally spaced by intervals of the same magnitude, correspond tothe duration of deenergization of the injectors at the end of eachinjection and more particularly to the duration of recovery of theflip-flop. By reason of such intrinsic properties these systems cannotoperate again for the next injection before the end of this recoveryperiod.

it is apparent then, that the storing period in the injection systemaccording to the invention is-not lost operative cycle and to provide anindividual throttling element in the admission pipe of each cylinder.This also results in eliminating the effect of the extent of overlappingof the valves engine on the reduced pressure. This results in aconsiderable advantage, since engines with a high specific power showgenerally a large overlapping of the valves which hitherto prevented theuse of sensors of reduced pressures for the production of a fundamentalregulating parameter and it was necessary to associate said parameterwith the opening angle of the gas throttling valve or valves with theconsequent necessity of introducing, as a fundamental parameter, thespeed of rotation of the engine through intricate means. 7 According tofurther developments of the principle of the invention, it is possiblefurthermore to constitute the detector of the angular position of theengine crankshaft by means of an electronic high frequency oscillatorpositioned in front of an element governed by the rotation of the engineand including one or more metal screens covering a predetermined angulararea said oscillator starting the absence of any screen and stoppingwhenever a screen registers with the oscillator. The oscillator feeds animpedance matching unit with two outputs, the first of which produces ahigh voltage level and the second of which produces a low voltage levelin the absence of oscillations whereas in the presence of oscillationsthe situation is reversed It is also provided with a direct output forthe oscillations;

employ as the threshold element a programcontrollable uni-junctiontransistor, the anode of which is connected with a condenser, thecathode of which is grounded or else connected with the base of atransistor controlling the end of the injection and and the controlelectrode of which is connected with the middle point of a voltagedivider;

employ as the threshold element a trigger with a plurality of inputs,one input being connected with a first memory defining a first referencevoltage for said trigger and the other with the input of the secondmemory defining a second reference voltage while the output of saidtrigger is connected with the amplifier controlling the electromagneticinjection valve or valves;

utilize switches comprising transistors operating as current generators,which in addition to functioning as switches, also adjust the rate ofcharging and discharging the condenser;

employ as switches electronic gates of the NAND )P apply a voltage tothe threshold element produced by a potentiometric voltage dividerforming a first memory adapted to store the information concerning theoperation of the engine;

comprise the first memory of a voltage divider connected through itsterminals with the high level and the low level outputs of thecrankshaft angular position detector, said voltage divider beingconnected through its middle point with the voltage supply through acondenser, said first memory being adapted to store information relatingto the rotary speed of the engine;

comprise the second memory of a condenser connected between the voltagesupply and theoutput of the detector and further connected with amonostable flip-flop triggered by the oscillations at the output of saiddetector, the width of the output signals of the monostable flip-flopbeing adjusted in conformity with the operative conditions of operationof the engine by a variable condenser, the second memory being furtherconnected with the collector of a transistor, the emitter of which isconnected with the voltage supply and the base of which is connectedwith the output of the detector, said second memory storing informationrelating to the load and speed of rotation of the engine.

generating the voltage on the lower terminal of the energy-and/orinformation-storing condenser by a voltage divider including resistancesand a transistor acting as a current generator;

feeding the base of said transistor a voltage governing the currentflowing through the transistor, said voltage being obtained by acapacitory divider including two condensers, one of which varies inaccordance with the operative conditions of the engine, said voltagedivider being connected with the output of the condenser on the one handand on the other hand through its middle point with the base of atransistor connected as an emitter follower, the emitter of which isconnected with the base of the current-generating transistor through arectifying diode, filtering resistances and a capacitance, the voltageapplied corresponding to the average value of the oscillations, theamplitude of which is defined by the capacitory divider;

connecting the energy and/or information-storing condenser emittercircuit of the current-generating transistor and a resistance betweenthe voltage supply and ground, the detecting oscillator being connectedthrough one of its outputs with the base of said transistor while thecharging voltage for said condenser is defined by the voltage dividerconstituted by a variable resistance and a fixed resistance, aprogramcontrollable uni-junction transistor being connected between thevoltage supply through the variable resistance and the fixed resistance,and the base of a transistor, the control electrode of theprogram-controllable uni-junction transistor being connected with theslider of a potentiometric voltage divider whereas the point throughwhich the resistances are connected is connected with the anode of thediode through the collector-emitter circuit of a transistor, the base ofwhich is connected with the cathode of the diode and also with thecollector through a resistance, the electromagnetic injection valve orvalves being controlled by an amplifier including transistors connectedwith the collector v of said last-mentioned transistor connecting theenergy and/or information storing condenser in series with a diode thecollector-emitter circuit of a transistor and a resistance between thevoltage supply and ground, the detecting oscillator being connected withthe base of said transistor through an impedance adaptor constituted bya condenser, a resistance and a transistor and through a capacitorydivider constituted by an fixed condenser and a variable condenserconnected between the collector of the transistor and ground, the middlepoint of said divider being connected with the base of a transistorconnected asan emitter follower and the emitter of which is connectedwith the base of the current generator transistor by a rectifying filterconstituted by a diode, resistances and a condenser, aprogram-controllable uni-junction transistor being connected in serieswith the emittercollector circuit of a transistor and a resistancebetween the voltage supply and the base of a transistor or ground, thecontrol electrode of said programcontrollable uni-junction transistorbeing kept at a predetermined voltage by means of a voltage dividerconstituted by. resistances, variable or fixed, while the anode of saidprogram-controllable uni-junction transistor is further connected withthe condenser through a diode, the base of the transistor in series withthe unijunction transistor being connected with the point connecting tworesistances with the collector-emitter program-controllable of a furthertransistor between the'feed supply and ground, the base of said furthertransistor being connected with the collector of a transistorincorporated with rectifying and filtering means constituted byresistances, a condenser and a diode and connected with the detectingunit so'as to form a control circuit, controlled by the condenser andresistances of the impedance adaptor;

controlling the electromagnetic injection valve or valves by anamplifier comprising a transistor, the base of which is connected withthe collector of the transistor controlling the end of the injection andis'grounded through a resistance, the base of said transistorcontrolling the end of the injection being connected with the cathode ofthe program-controllable uni-junction transistor while its emitter isgrounded.

By way of example and in order to further the understanding of thefollowing description of the invention, the accompanying drawingsillustrate said description. In said drawings:

FIG. 1 is a block diagram of the arrangement according to the invention;

FIG. 2 is a schematic diagram of the electronic control circuitaccording to a first embodiment.

FIG. 3 is a schematic diagram of the electronic control circuitaccording to a second embodiment;

FIG. 4 is a schematic diagram of the electronic control circuitaccording to a third embodiment.

Turning first to FIG. 1, it is apparent that the engine 85 provided withan intake manifold 87 is fed with fuel through the injectors comprisingby electromagnetic injection valves. In the case illustrated, there isprovided an indirect injection into the admission manifold 87, butobviously, the injection may be provided directly into the combustionchamber of the engine. Furthermore, the injection may be of a mechanicaltype beyond an electromagnetic injection valve controlled by theamplifier A. Obviously also, the fuel may be injected into the differentcylinders of the engine 85 either sequentially in accordance with thesequence of ignitions of the engine with the provision of a suitabledistributor which is not-illustrated, or else it may be injectedsimultaneously in all cylinders.

The injectors 20 are fed with fuel under constant pressure conditions bythe pump 92 drawing the fuel out of the tank 9l and delivering it intothe pipe 93 through the filter 89. The pipe 93 is provided with a 1 apressure regulator ing the injection in the memories M M and M which.

control the storing of injection energy in the memory M,. Said pulsegenerator further produces a signal of a predetermined duration duringwhich the injection takes place, said signal being transmitted to theampli fier A. The threshold element T +P is connected with the memoriesM M M and M, and may also be connected with the detector controlling theend of themjection through operation of the amplifier A. The unit -D, isan adaptor shaping the signals, and is used only in conjunction with theembodiment of FIG. 3 and the connections drawn in dashed lines are notessential for all embodiments. In FIG. 1, there is illustrated inputs ofall the operative parameters into the memory M But, obviously, saidparameters maybe introduced into any one of the memories or into allthree memories to be distributed in accordance with practicalrequirements.

In FIG. 2, there is illustrated a first practical embodiment of thecontrol arrangement wherein the detector D is constitutedby a unit 1provided with an output 8,, on which a positive voltage appears duringthe storing period. Said signal is applied to the base of a transistor 2forming a first switch C and the collector-emitter circuit of which isconnected in series with a resistance 6, a condenser 5 comprising theunit M a resistance 4, a diode 3'and another resistance 7 between thevoltage supply 23 and ground. The terminal A of the emitter of thetransistor is connected'with the voltage supply through the variableresistance 10 forming the memory M defining the charging level of thecondensers when the transistor 2 is conductive whereby the terminal A iskept at a voltage V which varies in accordance with the operativeconditions of the engine. The point A between the diode 3 and theresistance 4 is connected with a point A through the emitter-collectorcircuit of a transistor 8 forming a second switch C Said point A, isconnected with the base of the transistor 8 and with the collector ofthe transistor 2 through a resistance 9, with the voltage supply 23through the variable resistance 11 and withthe anode of aprogram-controllable uni-junction transistor or threshold unit T Pthrough a resistance 12. The variable resistance 11 forms'the memory Mcontrollingthe charging of the condenser 5 in accordance with theoperative condition of the engine. The control electrode of theprogramcontrollable uni-junction transistor 14 is connected with theslider of a potentiometric voltage divider 21 through a resistance 13,said voltage divider being connected between ground and the resistance22 connected with the voltage supply 23. This voltage divider forms thememory M, depending also on the operative condition of the engine. Thecathode of the programme-controllable uni-junction programcontrollableis connected with the base of a transistor 15 the emitter of which isgrounded and the collector of which is connected on the one hand withthe base of the transistor 16 forming part of the amplifier A and on theother hand with the voltage supply 23 through resistance 19.

The amplifier A further includes transistor 17 connected through itsbase with the collector of the transistor 16 and also with the voltagesupply through resistance 18.

The electromagnetic injection valves 20 are connected in series with theemitter-collector circuit of the transistor 17 between the voltagesupply and ground. The emitter of transistor 15 is also grounded.

The operation of the arrangement is as follows During the storing perioda high level signal appears at the output S, of the detector 1 andrenders the transistor 2 conductive. Consequently, the condenser 5 ischarged under a voltage corresponding to the difference between thevoltage V, of the supply of current and the voltage V defined by thevoltage divider constituted by the resistances 7 and 10. The chargingtime constant depends on the resistances 4 and 6 and on the capacity ofthe condenser 5. During this time, transistor 8 is cut off since thevoltage on its base is lower than that on its emitter.

When the detector enters its injection position, the signal at theoutput S, returns to its low level, which cuts off transistor 2.Therefore, transistor 8 becomes conductive since the voltage on its basemay rise to the value of the voltage at the point A,. Theprogramcontrollable uni junction transistor which had been conductive isthen cut off and condenser 5 discharges. The transistor 15 is also cutoff which renders the transistor 16 and 17 conductive and triggers theinjection. The condenser 5 during its discharge causes the voltage atthe point A, and consequently at the point A, to rise at a rate whichdepends chiefly on the value of the resistance 11. When the voltage atA, reaches a predetermined value with reference to the voltage appliedto the control electrode of the transistor 14, said programcontrollableuni-junction transistor 14 again becomes conductive which renders thetransistor 15 conductive and cuts off transistors 16 and 17, ending theinjection.

The programme controllable single junction transistor then remainsconductive until the next injection is initiated after a further storingperiod.

The duration of the injections thus depends on the charging voltage V,of the condenser 5, as defined by the resistance 10, the discharge speeddefined by the resistance 11 and by the reference voltage applied to thecontrol electrode of the programme-controlled unijunction transistor 14,which voltage is adjusted by the voltage divider 21. It is apparent thatthe resistance 10 acts on the very short storing period, while theresistance 11 and the potentiometer 21 are adapted to act during theinjection period. It is therefore possible to select the moment at whichthe engine parameters are introduced applied according to whether it ispreferable to cause their effect during the storing period or during theinjection period.

It should be noted that engine speed produces its effeet in the caseillustrated during the charging of the condenser. As a matter of fact,if the duration of the storing signal, which is inversely proportionalto the speed of rotation of the engine, is larger than about three timesthe time constant of the circuit charging condenser 5, said condenser isallowed a sufficient for reaching the asymptotic charging value. Thecharge consequently decreases when the speed of rotation rises above apredetermined limit while the duration of injection is reduced inaccordance with the speed of rotation beyond a predetermined threshold.

Obviously, the use of variable resistances for the adjustment of theduration of injection is not an optimum solution when it is desired toexecute speedy adjustments as simply as possible. 7

FIG. 3 illustrates a more complete, entirely transistorized circuit. Itshould be remarked that the unit 1 of the detector D comprises moreparticularly here a conventional electronic high frequency oscillatorwith the original feature being that it oscillates only when no metalmember is to be found in its vicinity. This feature is made use of byproviding in front of said unit 1, a rotary unit 86 (FIG. 1) controlledby the rotation of the engine and provided with alternating metallic andnonmetallic sectors. Over a predetermined angular area, the non-metallicsector or sectors cause the unit 1 to oscillate in conformity with thestoring period while the metallic sector or sectors produce a stoppingof the oscillations during a period corresponding to the injectionperiod. I

In the case of FIG. 3, the unit 1 is fed through the resistance 24, theresistances 26, 28, the condenser 25 and the transistor 27 forming animpedance matching adaptor provided on the collector of said transistor27 with an output terminal S on which the oscillations of the unit 1 arerepeated with a difference in phase.

The output terminal S is connected with a memory M constituted by acapacitory divider including a constant condenser 37 and an adjustablecondenser 38 connected in series between the output S and ground, theconnecting point between the condensers being connected with the base oftransistor 30 connected as an emitter follower grounded throughresistance 41 while its collector is connected with the voltage supply23. The emitter of the transistor 39 is further connected with thefiltering and rectifying circuit constituted by the diode 42, theresistances 43, 45, 47 and the condenser 44, the point connecting theresistances 45 and 47 being connected with the base of the transistor 2forming the first switch C, controlling the condenser 5. Said condenser5 is charged through the diode 3, the transistor 2 and the resistance 7while the charging voltage is defined by the voltage divider constitutedby the resistances 7 and 10a and by the voltage applied to the base ofthe transistor 2 which thus forms the memory M, with said voltagedivider 7-104 The condenser 5 is discharged through the transistor 50connected between the voltage supply 23 and the lower terminal of thecondenser, together with the resistance 51 and the diode 48. Saidtransistor 50 is controlled by the transistor 53 the collector of whichis connected with the base of the transistor 50 through the resistance52,the end of which connected with the base of the transistor 50 is alsoconnected with the voltage supply through the resistance 49. Thearrangement including elements 49 and 53 forms the switch C and thememory M The tering and rectifying unit constituted by the diode 31, theresistances 32, 34 and 35 and the condenser 33 is adapted to saturatethe transistor 36, the emittercollector circuit of which is connectedwith the resistance 46 between the voltage supply 23 and ground eachtime the unit 1 in the detector D oscillates. The collector of thetransistor 36 is connected with the base of the transistor 53 and,through the resistance 56, with the collector-base connection betweenthe transistors 15 and '16. I

The program-controllable uni-junction transistor 14 of the thresholdunit T P is connected through its anode with the point A,, through itscathode with the base of the transistor 15 and through its controlelectrode with the point connecting the resistance 21:; and 21bconnected in series between the voltage supply 23 and ground so as toform a voltage divider constituting the memory M,. The electromagneticinjection valves 20 are connected in parallel with the protecting diode55 in the collector-emitter circuit of the transistor 16 forming theamplifier A, between the voltage supply and ground. The base of thetransistor 16 in addition to its connection with the collector of thetransistor 15 is connected with ground through the resistance 54.

The operation of the circuit illustrated in FIG. 3 is similar to thatillustrated in FIG. 2. As a-rnatter of fact when the unit 1 oscillates,that is during the storing period, the oscillations after a phase shiftappear at the output terminal 8,, of the detector D. The capacitancevoltage divider constituted by the condensers 37 and 38 transmits theseoscillations to the transistor 39 connected as an emitter follower andthe amplitude of these oscillations is adjusted by the variablecondenser 38 in accordance with the operative condition of the engine.After the oscillations have passed through the rectifying and filteringunit 42-43-44-45, an average voltage appears on the base of thetransistor 2 connected as a current generator. The condenser 5 is thencharged through transistor 2 at a rate which depends on the voltage onthe base of said transistor 2 and at a level which depends on said basevoltage and on the resistances a and 7 in the collector-emitter circuitof the transistor 2.

At the same time, the oscillations at the output terminal S of thedetector D are transmitted to the rectifying and filtering means 31, 32,33, 34, 35 forming the unit D, in a manner such that the transistor 36is saturated. Consequently the transistor 53 is cut off and so is thetransistor 50. Furthermore transistor 16 is cut off by reason of itsconnection with the unit D, and therefore no injection can take place.

When the oscillations stop, that is during the injection period, thetransistor 2 is again cut off as is transistor 36 and the latter ensuresconductivity for the transistor 53 and consequently for the transistor50 connected as a current generator and controlling the discharge of thecondenser 5 at a rate depending on the current flowing throughtransistor 50.

Simultaneously, transistor 16 is saturated by reason of its connectionwith the unit D through the resistance 56 and this produces injection.The voltage at the point 'A, rises until it reaches a predeterminedvalue with reference to the voltage applied on the control electrode ofthe program-controllable uni-junction transistor 14, which triggers saidtransistor 14 and stops the injection since the transistor 15 becomesthen conductive and cuts off transistor 16. The transistor 14 remainsconductive since the transistors 53 and 50 remain conductive up to themoment at which further oscillations appear at the output terminal 8,and cause the transistors 53 and 50 to be cut off which cuts off thetransistor 14.

In the case considered, the fundamental regulating parameter such forinstance as the reduction in pressure in the admission manifold istransmitted to the condenser 38 which may be of a small capacity and bedesigned so as to vary inacco rdance with a suitable law with referenceto the reduction in pressure. Such a condenser has rapid response and issuitable therefore for the detection of rapid modifications of aparameter. The memory M introduces again a speed effect as in the caseof FIG. 2. The parameters which vary more 'slowly such as temperature oratmosphere pressure are introduced into the memories M, and/or M ltshould be noted that the amplifier A may be collected also by means of aconnection between the base of the transistor 16 and the middle point ofthe voltage divider 2la-2-1b of the memory through a resistance and byreplacing the resistance 56 by a diode.

FIG. 4 illustrates a control circuit constituted by integrated circuits.In fact, there is .provided a unit with four electronic gates of theNAND type, of which only three gates are made use of in association witha double trigger and a monostable flip-flop. [n this case, the circuitconnections are as follows The detector D includes the oscillator 1 fedthrough the resistance 24 followed by the filtering and rectifying meansconstituted by the resistances 26-30-74, the condenser 25-75, thetransistor 27 and the diode 73. The electronic gate 2a forming theswitch C, is connected through its input with the collector of thetransistor 27, while its output is connected with the input of thesecond electronic gate 53a forming the second switch C The output 8,, ofgate 2a and the output 8, of the gate 53a form the detector outputs. Thelevel of the output S, is low in the presence from oscillations of theoscillator 1 and the level of theoutput S is then high whereas, in theabsence of oscillations, the conditions are reversed. The output 8, ofthe detector D provides a direct connection for the oscillations of theoscillator 1. The output S, is connected to one of the inputs of a thirdgate 64 forming part of the threshold unit T P which further includes atrigger 65 the output g of which is connected with the other input ofthe gate 64 whereas the inputs e, and e of said threshold unit areconnected with the memories M, and M, respectively. The memory M, isconstituted by the resistances 21c and 21d connected in series betweenthe outputs S, and S, of the detector D with the interposition of thecorresponding diodes 63 and 66. Said memory M, further includescondenser 57 connected between the voltage supply 23 and the pointconnecting the resistances 21c and 21d with one another. The memory Mcomprises integrated bistable flip-flop 59 fed with triggering pulses toform the output 8,, of the detector D and through the condenser 72during the oscillations of the oscillator 1. The width of therectangular signals at the output of said flip-flop 59 is adjusted bythe variable condenser 60 in accordance with the fundamental regulatingparameter of the engine. The flip-flop 59 is connected with a condenser58 through the diode and the resistance 68, said condenser 58 beingfurther connected with the output S, of the detector D through theresistance 69 and the diode 71 and with the collector of the transistor61 while its other terminal is fed by the voltage supply 23. Thetransistor 61 is connected through its emitter with the supply 23through the resistance 76 and through its base with a voltage dividerconstituted by the resistances 77-78 connected between the voltagesupply 23 and ground, said base being further connected with the outputS through the diode 67. The energy-storing condenser is connectedbetween the voltage supply 23 and the output 8 said connection beingprovided through a resistance 7a and the diode 3. Said resistance 7aforms with the resistance a and the emitter-base circuit of thetransistor 2b the memory M which is a voltage divider defining the lowercharging voltage of the condenser 5. The resistance 10a is connectedwith the voltage supply 23 and with the emitter of the transistor 2b thebase of which is connected with the point joining the condenser 5 withthe resistance 7a. The collector of the transistor 2b is connectedthrough a resistance 62 with the base of the transistor 16 forming theamplifier A. transistor 16 has its collector emitter circuit connectedin series with the electromagnetic injection valve 20 between thevoltage supply 23 and ground. A protecting diode 55 is connected inparallel with the electromagnetic injection valve. A transistorconnected through its base with the output of the gate 64 has itscollector-emitter circuit connected between the base of the transistor16 and ground.

The integrated trigger 63 is associated with an identical independenttrigger 79, the latter ensuring constancy of the temperature of thecircuit. To this end, the inputs e and e of said trigger 79 are providedwith voltage dividers comprising the resistance 82 and the thermistance81 for e and two resistances 8384 for e The output 8 of the trigger 79is grounded through a heating resistance 80 fitted on the frameenclosing the circuits so as to heat them throughout when thethermistance has caused the trigger to change its condition to atemperature below a predetermined limit.

It should be noted that all the units provided with an integratedcircuit are fed with current by means which are not illustrated.

The operation of the injection-controlling system is as follows:

When the oscillator 1 oscillates during the storing period, the output Sis at a low level and the output S at a high level. Further, themonostable flip-flop 59 produces rectangular signals. Consequently, thetransistor 61 0f the memory M is cut of? and the condenser 58 is chargedthrough the voltage applied to its lower terminal, as defined on' theone hand by the voltage divider constituted by the resistances 69 and 68and on the other hand by the rectangular signals produced by theflip-flop 59. The charge on the condenser 58 depends therefore on thenumber of signals produced by said flip-flop 59 and on their width. Avoltage is applied to memory M during this time which corresponds to thecharge on the condenser 57 and depends on the duration of the storingperiod. Consequently, after a predetermined time trigger 65 changes itscondition, and produces at its output q a high level signal.

Since the gate 64 receives from the output S a low level signal itsoutput is at a high level which renders the transistor 15 conductive andcuts off transistor 16.

Simultaneously, the condenser 5 is charged at a rate defined by thetransistor 2b and the resistance 7a at a voltage level defined by thevoltage divider constituted by the resistances 7a and 10a.

At the beginning of the injection period, the output S rises to a highlevel while the output S falls to a lower level. The output S no longerfeeds any pulses to the flip-flop 50 so that its output remains at ahigh level which biases diode 3 and stops the charging of condenser 58if this charging has not ceased previously. This further results in gate64 receiving a high level signal which acts in association with the highlevel signal output of trigger 65 so as to make a low level signalappear at the output of gate 64, which signal cuts off transistor 15.Therefore, transistor 16 becomes conductive and initiates the injectionsince its base is fed by the transistor 2b which has also becomeconductive by reason of the lower voltage applied to its base.

During this time, condenser 58 is discharged through the transistor 61which has been rendered conductive by the low level signal applied toits base. The voltage applied to the input e, of the trigger 65consequently rises whereas the voltage applied to the input e, does notvary. This results in trigger 65 returning to its prior condition, whichcauses a low level signal to appear at its output q and a high levelsignal to appear at the output of the gate 64. The injection which istaking place is stopped by transistor 15 which becomes conductive andcut off base of the transistor 16.

It should be noted that in the FIG. 4 embodiment memories M, and M andthe unit M act on the injection as a function of engine speed. It istherefore possible, by a suitable selection of the various circuitcomponents, to obtain a duration of injection which in-.

creases first with low rotary speeds of theengine, remains at apredetermined level in the middle of the range of speeds and decreasesfor high speeds of rotatton.

As a matter of fact, for low speeds of rotation, condenser 57 isdischarged more slowly than the condenser 58 and there is obtained apositive speed effect, that is, the duration of the injection increases.In contradistinction for high rotary speeds, condenser 57 can no longerbe charged and a negative speed effect is obtained.

It should be further noted that the current passing through the injectoris governed by the amplifier A, that is by the transistor 16 the base ofwhich is fed by a current depending on the charge of the condenser 5 byreason of the connection between the base of the transistor 2b andcondenser 5. The end of injection is however defined by the outputsignal of gate 64 and consequently no difficulty can arise as far as theclosing of the injection valve 20 is concerned.

What I claim is:

l. A fuel injection system for an internal combustion engine adapted tooperate over a range of speeds and having an electrically actuable fuelmetering valve, said system comprising: i

a. a capacitor;

b. a charging circuit connected to said capacitor including: v

i. a power source having a substantially uniform output voltageconnected to said charging circuit for charging said capacitor,

ii. a first switch in said charging circuit which when closed enablescharging of said capacitor, the level of said charging being a functionof the duration of closure of said first switch, and

iii. first means for regulating the charging of said capacitor by saidcharging circuit when said first switch is closed as a function of afirst engine operating parameter,

0. means synchronized with engine rotational position for controllingsaid first switch means to close during a first predetermined portion ofthe engine cycle and to open said first switch means during a secondpredetermined portion of the engine cycle, the duration of the closingof said first switch by said controlling means varying as an inversefunction of the engine rotational speed, the duration of the closing ofsaid first switch at the higher engine rotational speed beinginsufficient to enable said first switch to charge said capacitor fullyand causing the charging of said capacitor to vary as an inversefunction to the engine rotational speed in at least a portion of therange of engine rotational speeds;

d. a discharging circuit connected to said capacitor including: I i. asecond switch the closing of which permits discharging of said capacitorthrough said discharging circuit,

ii. a reference point in said discharging circuit, said dischargingcausing the voltage at said reference point in said discharging circuitto change to a predetermined reference voltage in relation to the extentof the discharging, said second switch being closed in response to theopening of said first switch and opened in response to the closing ofsaid first switch by said first switch controlling means,

iii. second means for regulating the discharging of said capacitor bythe discharging circuit as a function of a second engine parameter,

e. threshold means connected to said reference point in said dischargingcircuit and being responsive to the voltage at said reference point foractuating the fuel metering valve only when said reference voltage is ina predetermined relationship with respect to a threshold level, thevalue of the threshold being determined by said threshold means, wherebythe duration of both the discharging of said capacitor to thepredetermined reference voltage and'the actuating of the fuel meteringvalve are a function of a level of charge obtained during the charging,the extent of discharging, and the value of the threshold level.

2. The apparatus of claim 1, in which said synchronized control meanscomprises:

a. an oscillator responsive to an input to produce a signal,

b. a detector responsive to rotation of the engine to produce said inputonly during said first portion of the cycle, and

c. means connecting said oscillator to said first and second switches toapply said signal to close said first switch and open said second switchresponsive to the presence of said signal and to close said secondswitch and open said first switch responsive to the absence of saidsignal during said second portion of the cycle. 3. the apparatus ofclaim 1 in which said threshold means comprises:

a. an amplifier connected to the fuel valve for actuating the valve inresponse to-an input to said amplifier,

b. a three-terminal semiconductor gating element having two mainterminals between which current easily passes in a forward directiononly when said gating element is fired, and a gate terminal forcontrolling the firing point of said gate element, the main terminals ofsaid gating element being connected in said forward direction betweensaid reference point and said amplifier for providing said input onlywhen said gating element is firing, and a variable output voltagedivider having its output connected to the gate terminal of said gatingelement for controlling its firing point, the value of said variableoutput b'eing dependent on the value of a third engine operatingparameter,

whereby the duration of actuation of the fuel valve is further dependenton the output value of the voltage divider which is in turn dependent onsaid third parameter.

4. The apparatus of claim I, in which said threshold means comprises:

a. an amplifier for actuating the fuel valve in response to an input,

b. a trigger connected between said reference point and said amplifierto provide said amplifier input when said reference voltage is less thansaid threshold level, and

c. threshold-setting means connected to said trigger and responsive to athird engine parameter for determining said threshold level.

5. The apparatus of claim 1 in which each of said first and secondswitches comprise a transistor, which transistors are connected ascurrent generators to control said rates of charging and discharging,respectively.

6. The apparatus of claim 1, in which each of said first and secondswitches comprises an electronic NAND gate.

7. The apparatus of claim 3, in which said voltage divider comprises apotentiometer.

8. The system of claim 4, in which said thresholdsetting means comprisesa voltage divider connected between the output of said detector and alow voltage point, the midpoint of said voltage divider connectedbetween said trigger and a source of electric potential via a capacitor.

9. The system of claim 1, in which said second means comprises:

a. a flip-flop connected at its input to the output of said synchronizedcontrol means said flip-flop being adapted to produce a square waveoutput having a frequency equal to that of said synchronized controlmeans output, I

b. means including a variable capacitor connected to said flip-flop, thevalue of said variable capacitor determining the breadth of said squarewaves, the value of said variable capacitor being dependent on saidsecond parameter,

c. a fixed capacitor connected between the output of said flip-flop andsaid power source, and

d. a transistor having its collector-emitter circuit connected betweensaid power source and the output 5 tion of engine speed and of the valueof said second pal 16 b. said first means comprises a voltage dividerconand ground,

nected between said Power Source and ground, the ii. an emitter-followertransistor having its base midpoint of said voltage divider beingconnected to the terminal of said capacitor nearest ground.

volta e divider and 11. The system of claim 1, in which: 5 g a. Saidfirst Switch comprises a first transistor in. a rectifier-filter circuitconnected between the i fi means comprises; emitter of saidemitter-follower transistor and the i. a capacitive voltage dividerconnected between base of Said fi l gn istorthe output of saidsynchronized control means connected to the midpoint of said capacitive.UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,7414,1460 Dated Jul-y '10) 1973 Iziventor s) Louis Monpet it It: iscertified that error appears in theabOVe-iden-tified patent and thatsaid Letters Patent are hereby corrected as shown below: I

Columri l, line. 12, change solenoid actuated "Pi ot 1 solenoid actuated Column 1, line 20, Change "solenoid-actuated: fuel injector.valve" to solenoid-actuated fuel, "injection valves I Column 1, line"21;, "iinsert' an before "amplifier' f. Column *line 21; delete [ax 1]before ':'a.c cx ire. fcle Column l, linei363 change "admission" 1 20 ih t ke -Ii Column-1; i e-57- fde- I wer re "step".

column'l, 1 1x59, delete [said]; I

. Column 2*, line"-"67',I hange; "pe iod?! to pg ridg d Column ZQ I T B-S S, Y change last-mentioned" s d fio f-. said i last-mentioned 1 Columnline l-l8 a aftefprever s'ed ineerjQIIaQQtf C.

u n 35 n "P r I UNITED STATES PATENT. mm: v e e CERTIFICATE'OFCORRECTION Patent No. 3,7MJ -6O v Dated 10 "197 3 Imrentmfls) Monpetit vv Mj Itis certified that error appears in the above-identified patentand that said Letters Patent are hereby @orrected as shown below:

Column 4, line 32, change "transistor aIvo' lta'ge" to read transistorwith a. voltage. Y V Colunn 4, line #7, after "condenser" insert :4 inseries with resistances, a. diode, the collector- I emitter o mn Ql 57,ange "program" togpro gramm' Column 5, line '15; change 'program ,toprogramme 59-;

Column 5, line 27 after "two? insert series Q Column, 5, line 28, change"program" to programme -51.

Column 5, 'lines' 28 and 29, change programcontrollable10f a.

further transistor between the feed supply and ground, the base, of saidfurther to circuit of a. further transistor between: the voltage supplyand ground, .theibase of s a.id further r v l'u '5, 3 3- ypr ogz 'amjcontroll able7' ....n. I v i I programmecontrollable Y coiunmffj,"line142; change program to programme -F;

' Column 5,;line 19, onenge "program" to 1-fprogx amne' m-g I *UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 74 4, 460Dated July 10. 1973 -3- Inventor(s) LOLIlS Monpetlt I It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below: 7

Column 5, line 23, change "program" to programme Column 6, line 5 change"program" to programme Column 6, line 59 change "program' to programmeColumn 6, line 67, I change "program" to programme Column 6, line 67,cancel "programl w Column 7, line 1, change "controllable" to transistorColumn 7, lineal, change "program" to programme Column 7; lille' 32,change "uni junction" .to uni-junction Column 7, line ll change"program" to programme Column 7, line 45 a change "single to Column 7,line 59, delete [introduced].

Column 8, line 37, change "30" t 39 Column 9, line ll, 7 change"program" to v rogramme Column 9, line 6%, change "program' to vprogramme 7- Column 10, lines 17 and 18, 7 change "collected" tocontrolled STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,74%460 DatedJuly 10, 1973 Patent No.

Louis Monpetit Inventor(s) It is certified that error appears in theabove-'-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 10, line 32, change "2a." to 2Q- Column 11, line 2, before "sup lnge voltage Column 11, line 28, change' '63" 130 65 1} Column 12, 7 lineA, change "50 to 59,

Column 12, line 25, change "cutoff base of the" to cuts off transistor16..--. I

Signed and sealed this 22nd day of January 1974.

""Attest:

'EDWARD M.FLETC IHER,JR. RENE D. TEGTMEYER Attestlng Offlcer ActingCommissioner of Patents

1. A fuel injection system for an internal combustion engine adapted tooperate over a range of speeds and having an electrically actuable fuelmetering valve, said system comprising: a. a capacitor; b. a chargingcircuit connected to said capacitor including: i. a power source havinga substantially uniform output voltage connected to said chargingcircuit for charging said capacitOr, ii. a first switch in said chargingcircuit which when closed enables charging of said capacitor, the levelof said charging being a function of the duration of closure of saidfirst switch, and iii. first means for regulating the charging of saidcapacitor by said charging circuit when said first switch is closed as afunction of a first engine operating parameter, c. means synchronizedwith engine rotational position for controlling said first switch meansto close during a first predetermined portion of the engine cycle and toopen said first switch means during a second predetermined portion ofthe engine cycle, the duration of the closing of said first switch bysaid controlling means varying as an inverse function of the enginerotational speed, the duration of the closing of said first switch atthe higher engine rotational speed being insufficient to enable saidfirst switch to charge said capacitor fully and causing the charging ofsaid capacitor to vary as an inverse function to the engine rotationalspeed in at least a portion of the range of engine rotational speeds; d.a discharging circuit connected to said capacitor including: i. a secondswitch the closing of which permits discharging of said capacitorthrough said discharging circuit, ii. a reference point in saiddischarging circuit, said discharging causing the voltage at saidreference point in said discharging circuit to change to a predeterminedreference voltage in relation to the extent of the discharging, saidsecond switch being closed in response to the opening of said firstswitch and opened in response to the closing of said first switch bysaid first switch controlling means, iii. second means for regulatingthe discharging of said capacitor by the discharging circuit as afunction of a second engine parameter, e. threshold means connected tosaid reference point in said discharging circuit and being responsive tothe voltage at said reference point for actuating the fuel meteringvalve only when said reference voltage is in a predeterminedrelationship with respect to a threshold level, the value of thethreshold being determined by said threshold means, whereby the durationof both the discharging of said capacitor to the predetermined referencevoltage and the actuating of the fuel metering valve are a function of alevel of charge obtained during the charging, the extent of discharging,and the value of the threshold level.
 2. The apparatus of claim 1, inwhich said synchronized control means comprises: a. an oscillatorresponsive to an input to produce a signal, b. a detector responsive torotation of the engine to produce said input only during said firstportion of the cycle, and c. means connecting said oscillator to saidfirst and second switches to apply said signal to close said firstswitch and open said second switch responsive to the presence of saidsignal and to close said second switch and open said first switchresponsive to the absence of said signal during said second portion ofthe cycle.
 3. the apparatus of claim 1 in which said threshold meanscomprises: a. an amplifier connected to the fuel valve for actuating thevalve in response to an input to said amplifier, b. a three-terminalsemiconductor gating element having two main terminals between whichcurrent easily passes in a forward direction only when said gatingelement is fired, and a gate terminal for controlling the firing pointof said gate element, the main terminals of said gating element beingconnected in said forward direction between said reference point andsaid amplifier for providing said input only when said gating element isfiring, and c. a variable output voltage divider having its outputconnected to the gate terminal of said gating element for controllingits firing point, the value of said variable output being dependent onthe value of a third engine operating parameter, whereby the duration ofactuation of the Fuel valve is further dependent on the output value ofthe voltage divider which is in turn dependent on said third parameter.4. The apparatus of claim 1, in which said threshold means comprises: a.an amplifier for actuating the fuel valve in response to an input, b. atrigger connected between said reference point and said amplifier toprovide said amplifier input when said reference voltage is less thansaid threshold level, and c. threshold-setting means connected to saidtrigger and responsive to a third engine parameter for determining saidthreshold level.
 5. The apparatus of claim 1 in which each of said firstand second switches comprise a transistor, which transistors areconnected as current generators to control said rates of charging anddischarging, respectively.
 6. The apparatus of claim 1, in which each ofsaid first and second switches comprises an electronic NAND gate.
 7. Theapparatus of claim 3, in which said voltage divider comprises apotentiometer.
 8. The system of claim 4, in which said threshold-settingmeans comprises a voltage divider connected between the output of saiddetector and a low voltage point, the midpoint of said voltage dividerconnected between said trigger and a source of electric potential via acapacitor.
 9. The system of claim 1, in which said second meanscomprises: a. a flip-flop connected at its input to the output of saidsynchronized control means said flip-flop being adapted to produce asquare wave output having a frequency equal to that of said synchronizedcontrol means output, b. means including a variable capacitor connectedto said flip-flop, the value of said variable capacitor determining thebreadth of said square waves, the value of said variable capacitor beingdependent on said second parameter, c. a fixed capacitor connectedbetween the output of said flip-flop and said power source, and d. atransistor having its collector-emitter circuit connected between saidpower source and the output of said flip-flop and its base connected tothe output of said synchronized control means, whereby the voltage onsaid fixed capacitor is a function of engine speed and of the value ofsaid second parameter.
 10. The system of claim 1, in which: a. saidfirst switch comprises a first transistor, and b. said first meanscomprises a voltage divider connected between said power source andground, the midpoint of said voltage divider being connected to theterminal of said capacitor nearest ground.
 11. The system of claim 1, inwhich: a. said first switch comprises a first transistor, b. said firstmeans comprises: i. a capacitive voltage divider connected between theoutput of said synchronized control means and ground, ii. anemitter-follower transistor having its base connected to the midpoint ofsaid capacitive voltage divider, and iii. a rectifier-filter circuitconnected between the emitter of said emitter-follower transistor andthe base of said first transistor.